To swipe more than one item at a time, go to js/main.js and find this function, function clientsCarousel(){. Inside the function code you have this line: scroll: { items : 1 },
Just change the value to the number of items you want to scroll. Example: scroll: { items : 4 }, will scroll 4 items at a time.
Transition duration is not responsible for the clients speed, but the animation duration of the client logo showing up (not scroll).
